Solving the Cooling Flow Problem through Mechanical AGN Feedback
Solving the Cooling Flow Problem through Mechanical AGN Feedback
复制标题
通过机械 AGN 反馈解决冷却流问题
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
M. Ruszkowski
中科院分区：
文献类型：
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作者：
M. Gaspari;F. Brighenti;M. Ruszkowski
等离子体的非对抗性辐射冷却将导致冷却灾难，即大量凝聚气体流入星系、星系群和星系团的核心。上一代X射线望远镜Chandra和XMM从根本上改变了我们对重子的看法，表明活动星系核的加热是冷却的平衡。这项工作回顾了我们对自我调节供暖的广泛研究。我们认为，基于大量亚相对论外流的机械反馈是解决冷却流动问题的关键，即在不破坏冷核结构的情况下，对几个回旋体的冷却速率进行动态冷却。利用修改后的三维流体程序Flash，我们证明了双极活动星系核的外流可以进一步再现基本的观测特征，如浮泡、弱激波、金属淤积和湍流。后者是驱动非线性热不稳定性的基本因素，非线性热不稳定性导致扩展的冷气的形成，这是淬火冷却流的残留物，然后是反馈发动机的燃料。与星系团相比，星系群和星系需要更温和的机械反馈，以避免灾难性的过热。我们强调了现实活动星系核反馈的基本特征，强调了观测的一致性。
Unopposed radiative cooling of plasma would lead to the cooling catastrophe, a massive inflow of condensing gas, manifes t in the core of galaxies, groups and clusters. The last genera tion X-ray telescopes, Chandra and XMM, have radically changed our view on baryons, indicating AGN heating as the balancing counterpart of cooling. This work reviews our extensive investigation on self-regulated heating. We argue that the mechanical feedback, based on massive subrelativistic outflows, is the key to solving the cooling flow problem, i.e. d ramatically quenching the cooling rates for several Gyr without destroying the cool-core structure. Using a modifie d version of the 3D hydrocode FLASH, we show that bipolar AGN outflows can further reproduce fundamental observed fea tures, such as buoyant bubbles, weak shocks, metals dredgeup, and turbulence. The latter is an essential ingredient to drive nonlinear thermal instabilities, which cause the for mation of extended cold gas, a residual of the quenched cooling flow a nd, later, fuel for the feedback engine. Compared to clusters, groups and galaxies require a gentler mechanical feedback, in order to avoid catastrophic overheating. We highlight the essential characteristics for a realistic AGN feedback, wi th emphasis on observational consistency.